Overexpressed Yeast Bax Inhibitor (Bxi1p/Ybh3p) is a Calcium Channel in <i>E. coli</i>

Mullin, James; Kalhorn, John; Aguilar, Julia; Crago, Madelyn; Mello, Nicholas; Raffa, Amanda; Strakosha, Alexander; Austriaco, Nicanor O.P.

VOLUME 17 (Supplement)

SciEnggJ%202024%20Special%20Issue%201 7 Pasham%20et%20al

SciEnggJ 17 (Supplement) 036-041
available online: February 28, 2024
DOI: https://doi.org/10.54645/202417SupUEV-94

*Corresponding author
Email Address: naustriaco@ust.edu.ph
Date received: December 14, 2023
Date revised: January 21, 2024
Date accepted: January 25, 2024

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ARTICLE

Overexpressed yeast Bax inhibitor (Bxi1p/Ybh3p) is a calcium channel in E. coli

James Mullin¹, John Kalhorn¹, Julia Aguiar¹, Madelyn Crago¹, Nicholas Mello¹, Amanda Raffa¹, Alexander Strakosha¹, and Nicanor Austriaco, O.P.*^1,2,3,4

¹Department of Biology, Providence College, Providence RI 02918 USA
²Department of Biological Sciences, University of Santo Tomas, Manila
     1015 PHILIPPINES
³UST Laboratories for Vaccines Science, Molecular Biology, and
     Biotechnology, University of Santo Tomas, Manila 1015 PHILIPPINES
⁴Research Center for the Natural and Applied Sciences, University of Santo
     Tomas, Manila 1015 PHILIPPINES

KEYWORDS: Bax Inhibitor, Bxi1p, Ybh3p, calcium channel, TMBIM6, BI-1

Human Bax Inhibitor-1 (HsBI-1/TMBIM6) is the founding member of the evolutionary conserved TMBIM superfamily of proteins that share sequence homology within the transmembrane Bax inhibitor-containing motif (TMBIM). Mechanistically, BI-1/TMBIM6 and all the other mammalian TMBIM proteins appear to be involved in the maintenance of calcium homeostasis, and the crystal structure of a bacterial TMBIM protein, BsYetJ, suggests that the protein is a pH-sensitive calcium leak. The budding yeast, Saccharomyces cerevisiae, has a single TMBIM family member (YNL305C) named Bxi1p/Ybh3p. To determine the function Bxi1p/Ybh3p, we overexpressed Bxi1p-GFP in E. coli to interrogate its putative calcium channel function. We show that bacterial cells expressing Bxi1p-GFP are more permeable to calcium than controls. Our data suggests that yeast Bax inhibitor (Bxi1p) is a calcium channel in E. coli, lending support to our proposal that Bxi1p is a bona fide member of the TMBIM family of proteins. Finally, parallel experiments also revealed that the human Bax Inhibitor-1 (HsBI1/TMBIM6) is also a calcium channel in bacteria.